package javax.annotation;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import javax.annotation.meta.TypeQualifier;
import javax.annotation.meta.TypeQualifierValidator;
import javax.annotation.meta.When;

/** Used to annotate a value that should only contain nonnegative values */
@Documented
@TypeQualifier(applicableTo = Number.class)
@Retention(RetentionPolicy.RUNTIME)
public @interface Nonnegative {
  When when() default When.ALWAYS;

  class Checker implements TypeQualifierValidator<Nonnegative> {

    public When forConstantValue(Nonnegative annotation, Object v) {
      if (!(v instanceof Number)) return When.NEVER;
      boolean isNegative;
      Number value = (Number) v;
      if (value instanceof Long) isNegative = value.longValue() < 0;
      else if (value instanceof Double) isNegative = value.doubleValue() < 0;
      else if (value instanceof Float) isNegative = value.floatValue() < 0;
      else isNegative = value.intValue() < 0;

      if (isNegative) return When.NEVER;
      else return When.ALWAYS;
    }
  }
}
